[PHNUTR-L] Study with smokers shows vitamins C, E, combine for benefits

[Kathrynne Holden, MS, RD]

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Public release date: 15-Feb-2006
http://www.eurekalert.org/pub_releases/2006-02/osu-sws020906.php

Contact: Maret Traber
maret.traber at oregonstate.edu
541-737-7977
Oregon State University

Study with smokers shows vitamins combine for benefits

A new study has found that supplements of vitamin C can largely stop the 
serious depletion of vitamin E that occurs in smokers, demonstrating for 
the first time in humans a remarkable interaction between these two 
antioxidants as they work together.

The research also suggests a possible mechanism by which smoking can 
cause cancer.

The findings are being published today in Free Radical Biology and 
Medicine, a professional journal, by scientists from the Linus Pauling 
Institute at Oregon State University.

The results of the research were based on a placebo-controlled, 
double-blind clinical study with smokers and non-smokers, and showed 
that supplements of 1000 milligrams of vitamin C per day could reduce by 
up to 45 percent the rate of disappearance of one form of vitamin E in 
smokers. In general, vitamin C supplements helped protect the function 
and plasma levels of vitamin E, so that smokers who took supplements had 
about the same level of antioxidant protection as non-smokers.

"A lot of nutrition research in the past has been done by studying one 
nutrient or another in isolation, sometimes with conflicting results," 
said Maret Traber, a professor of nutrition at OSU and lead researcher 
in the Linus Pauling Institute. "What this and other studies like it are 
showing is that the protection we get from proper diet or supplements 
often comes from combinations of nutrients working together. This has 
implications not only for smokers but also for many other people."

Vitamin E is one of the first lines of defense in human lung tissue 
against the ravages of cigarette smoke, Traber said, which creates 
destructive free radicals. If the body has adequate levels of vitamin E, 
this protective antioxidant can interact with the peroxyl radicals 
created by cigarette smoke and prevent the destruction of lung membranes.

In this process, however, vitamin E can itself be made into a 
destructive radical. If adequate levels of vitamin C are present, it can 
help the vitamin E return to non-radical form and continue its 
protective role. But in the absence of adequate vitamin C, this process 
breaks down. The new study is one of the first to ever demonstrate this 
phenomenon in humans.

This and other studies at the Linus Pauling Institute have also shown 
that in smokers, vitamin E is being depleted from tissue concentrations 
in order to keep up its levels in the blood.

"We've known for some time that smokers are under oxidative stress, 
because the smoke itself is an oxidant that creates free radicals and 
cell mutations," Traber said. "The immune response of the body also 
tends to cause inflammation, and this inflammation is one reason that 
smoking relates not only to lung cancer but other serious health 
problems such as diabetes, hypertension and heart disease."

By having a more rapid loss of protective antioxidants, Traber said, 
smokers face special challenges.

"Think of a bucket that's filled with water but has holes in it," she 
said. "If you want to keep the water level, you have to keep adding 
water. But with smokers, the holes in the bucket are bigger and the 
water level goes down faster. In the case of nutrition, you have to add 
more and more nutrients to stay even."

With smokers, she said, that rarely happens. In the general population, 
research has shown that only 8 percent of men and 2.4 percent of women 
have adequate dietary intake of vitamin E. And studies indicate that 
smokers often have a diet with lots of meat but low intakes of the 
fruits and vegetables that provide most antioxidants. So although 
smokers require higher levels of antioxidants to gain their protective 
benefits, their diets usually contain even lower dietary intakes than 
most people – and nearly 50 million Americans smoke cigarettes.

For antioxidant vitamins to play a role in disease prevention, experts 
say, they usually have to be present in advance. They are less 
successful in addressing existing disease. According to Traber, many of 
the studies showing "no benefit" from improved nutrition or vitamin 
supplements have been done in people with existing disease, or studying 
one nutrient at a time rather than combinations.

In this research, participants were asked to eat a diet low in fruits 
and vegetables for three months so they had low levels of vitamin C. 
Some members were then given vitamin C supplements, and others a 
placebo. Smokers who got vitamin C supplementation had a plasma vitamin 
E disappearance rate about the same as non-smokers. But smokers who were 
still deficient in vitamin C lost alpha vitamin E about 25 percent 
faster than non-smokers, and gamma vitamin E about 45 percent faster.

Other collaborators on this research were from Columbia University, The 
Ohio State University, the University of Washington, and Brock 
University in Canada. Richard Bruno, a doctoral student at The Ohio 
State University, was also a co-author. The research was funded by the 
National Institutes of Health.

"What this clearly shows is that to perform their vital roles, vitamins 
C and E work together," Traber said. "They have a synergistic effect 
that will not be gained just by intake of one or the other, and adequate 
levels of these nutrients is especially important for people who smoke."
-- 
Kathrynne Holden, MS, RD < fivestar at nutritionucanlivewith.com >
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